Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved is not to be classified under H04S 1/00 but under H04S 3/00, H04S 5/00 or H04S 7/00 using the Indexing Code H04S 2400/01.

Further detail is covered by the subgroups of Indexing Code group H04S 2400/00 and H04S 2420/00. Classification is obligatory.

{Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution (control circuits for electronic adaptation of the sound field H04S 7/30)}

Definition statement

This subgroup covers:

Electronic sound processing for enhancing the sound image or the spatial distribution, wherein the processing itself is independent on the input signal or its properties.

See for example: WO2005009078

References relevant to classification in this subgroup

This subgroup does not cover:

Control circuits for electronic adaptation of the sound field, i.e. electronic sound processing automatically adaptable in dependence of the input signal or some of its properties, e.g. by using an adaptive circuit or a look-up table, for changing the sound field, e.g. the spatial distribution

{Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution (control circuits for electronic adaptation of the sound field H04S 7/30)}

Definition statement

This subgroup covers:

Electronic sound processing for enhancing the sound image or the spatial distribution, wherein the processing itself is independent on the input signal or its properties.

See for example: US5740253

References relevant to classification in this subgroup

This subgroup does not cover:

Control circuits for electronic adaptation of the sound field, i.e. electronic sound processing automatically adaptable in dependence of the input signal or some of its properties, e.g. by using an adaptive circuit or a look-up table, for changing the sound field, e.g. the spatial distribution

Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation (arrangements for producing a reverberation or echo sound G10K 15/08)

{Control circuits for electronic adaptation of the sound field (non-adaptive circuits, i.e. manually adjustable or static, for enhancing the sound image or the spatial distribution H04S 1/002, H04S 3/002)}

Definition statement

This subgroup covers:

Electronic sound processing automatically adaptable in dependence of the input signal or some of its properties, e.g. by using an adaptive circuit or a look-up table, for changing the sound field, e.g. the spatial distribution.

Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF’s] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]